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Shoulder Muscles

Muscles of the shoulder cross the ________ ________ to insert into the ______.

Therefor, the muscles of the ______ move the ______.

The muscles of the shoulder cross the shoulder joint to insert into the arm. therefor the muscles of the shoulder move the arm. Remember, to cause movement: a muscle must cross a joint.

Muscles crossing the shoulder Joint:

6 Intrinsic Shoulder Muscles

Shoulders Should (Throw-Many)^2 Inflatable Disks

Subscapularis
Supraspinatus

Teres Major
Teres Minor

Infraspinatus
Deltoid

3 parts that cross shoulder joint and move the arm

1 anterior thorax: _____________
1 Posterior Thorax: ___________
1 Small anterior Arm: _________

1 anterior thorax: Pectoralis Major
1 posterior thorax: Latisimus dorsi
1 small atnerior arm: Coracobrachialis

Pectoralis Major

Shape?
2 heads: ___ and ____
Forms anterior wall of _____

Powerful Adductor and Medial Rotator

LArge Fan shaped Muscle.

2 heads: clavicular and sternal.

Forms anterior wall of axilla.

Powerfull adductor and medial rotator.

Pec Major.
-Covers superior part of thorax.
-pec minor is underneath (deep) to this.
-Small portion starts at clavicle. large poirtion os from sternum. they form the anterior wall of axilla (anterior axillary fold).
-Pec major is a powerful adductor of ARM and medial rotator of HUEMRUS.
-if you adduct the arm against force, the anterior axiallary force becomes taunt. the two parts of this muscle can act independently. raise your arm 90 degrees and adduct it against force, the clavicular head can be palpated. raise it 60 degrees and forcefully adduct it and sternal head can be palpated.

-Origin: begins off clavicle, sternum, and ribs 1-6 cartilage.

-Inserts: into intertubercular solcous of humerus.

-Intervated: by lateral and medial pectoral nerve which arise from brachioplexis.

-Pectoralis major flexes, adducts and rotates the humerus medially.

Latissimus Dorsi

Widest of the back.

Does THREE things to humerus

Forms Posterior Axillary Fold

Widest of the back.

Does THREE things to humerus
Extends, Retracts, and Rotates the humerus Medially.

Forms Posterior Axillary Fold


-large fan shaped and covers most of lower half of back.
-goes from trunk to humerus.
-helps to form posterior axillary fold.
-The latissiumus dorsi extends, adducts , and rotates the humerus medially, such as in scratching the skin in the opposite scapula. take right hand and bring it back to touch scapula on left side. you need to extend humerus, adduct humerus, and rotate it medially.
-working with the pectoralis major, the latismus dorsi is a powerful adductor of humerus. it is important for restoring the upper limb to shoulder from an abducting position like in climbing.
- the latissimus dorsi also raises the trunk to the arm like in doing pull ups.

-to test the latissimus dorsi or it's nerve, the arm is abducted 90 degrees. and when adducted against resistence you can feel the posterior axilarry fold if it is normal.

-Origin: thoraco lumbar or lumbo dorsho fasha. it is a wide band of fasha like an aparossis, which originates of the spinous processes of T7-T12, the lumbar vertebrae, the illiac crest , and sometimes of the inferior angle of scapula.

-The muscle extends laterally and inserts into the intertobucular groove of the humerus.

-it is intervated by the thoracodorsal nerve.

-it's action is that it is a powerful extensor of humerus, a powerful adductor, and a medial rotator of the arm. it also helps to depress the shoulder.

Triangle of Ausculation.

Lateral border:
Medial Border:
Lower Border:

Lateral border: Scapula
Medial Border: Trapezius
Lower Border: Latissimus Dorsi


This is not covered by any thick muscle. so you can HEAR THE LUNGS. it also helps with identifying the location of muscles in relationship with each other. the trapezius lies medial and superior to latisimus dorsi, the scapula lies lateral to trapezius and the latisimus dorsi lies inferior to both of those.

Deltoid

3 parts act together to _____ the arm.

Anterior Part Flexion and Medial Rotation

Posterior part extension and lateral rotation

Inter muscular injections.

Deltoid.
-Forms rounded part of shoulder. shaped like an inverted delta.
-3 parts.
-when they act together = Abduct the arm.
-anterior fibers aid the pec major in flexing the arm.
-post fibers aid the latismus dorsi in extending the arm.
-the anterior and posterior fibers swing the arm during walking.
-deltiod helps to stablize the shoulder joint and hold the head of humerus in the glenoid cavity during shoulder movement.
-to test it, arm is abducted 15 degrees and it is abducted against resistence. if the muscle and the nerve to the muscle (axilary) are intact, the deltoid can be easily seen and palpated.
-common site for intramuscular injection of drugs.
-the muscle is well developed. axilary runs deep from behind. if axilary enters from behind, you should give the injection ____?-The deltoid originates from the lateral 1/3 of clavicle, from the acromium process, and from lateral aspect from the spine of scapula.
-it inserts into a tuberosity on the humerus' deltoid tuberosity.
-it is invervated by the axilary nerve, a branch of brachioplexis. it is important for abduction of the arm especially above 15 degrees.
-Superspinatous: responsible for initiating abduction (first 15 degrees of abduction).
-The anterior fibers of the deltoid flex the arm and posterior fibers extend the arm.
-The anterior fibers also help in medial rotation and posterior help in lateral rotation.

Subscapularis
Fills in subscapular Fossa,
Underneath the scapula.

Inserts into _______ tubercle

Primary medial Rotater of the arm

Rotator Cuff muscle: Holds head of humerus in glenoid cavity.

Subscapularis
Fills in subscapular Fossa,
Underneath the scapula.

Inserts into lesser tubercle

Primary medial Rotater of the arm

Rotator Cuff muscle: Holds head of humerus in glenoid cavity.

-subscapularis helps to form part of the posterior axillary fold along with the latissimus dorsi.
-subscapularis inserts into lesser tubercle of humerus. is the primary medial rotator of the arm and helps in adduction.
-works with other rotator cuff muscles to help hold head of humerus in the glenoid cavity during movement.
-origin: deep side of scapula. from the subscapular fossa (costal surface of scapula).
-fibers extend laterally to insert on lesser tubercle of humerus.
-it is intervated by subscapular nerve.
-priimary action is medial rotation of humerus.

Supraspinatus

Must reflect the ______ and ______ to see this muscle.

Initiation of arm abduction, after 15 degrees.. deltoid becomes effective.

Rotator Cuff Muscle

Inserts into _______ tubercle.

Supraspinatus

Must reflect the trapezius and deltoid to see this muscle.

Initiation of arm abduction, after 15 degrees.. deltoid becomes effective.

Rotator Cuff Muscle

Inserts into greater tubercle.

Supraspinatus Muscle.
-Occupies the supraspinous fossa.
-inserts into the greater tubercle of humerus.
-to view it entirely, deltoid and trapezius must be reflected
-to test it : arm is abducted against resistance from a fully adducted position. this is the muscle that initiates adduction. once the arm is moved more than 15 degrees from the body, the deltoid is effective and provide abduction for this movement. you can palpate it superior to the spine of scapula. this is one of the rotator cuff muscles.
-It's origin is from supraspinous fossa of scapula.
-it inserts into the greater tubercle of humerus.
-it is intervated by the superscapular nerve.
-action is abduction of arm. especially the first 15 degrees (initiation of abduction).
-also helps to stabilize the shoulder during rotation.
-helps prevent downward dislocation of humerus (ex: carrying heavy bag. helps to hold humerus into glenoid cavity. )

Which muscle inserts into greater tubercle?

Which into lesser tubercle?

Subscapularis = lesser

Infraspinatus, Supraspinatus = greater

Infraspinatus

Occupies infraspinous fossa.

Reflect ______ and _____ to see it.

Powerful Lateral Rotator

ROTATOR CUFF MUSCLE.

Inserts into greater tubercle of ________

Occupies infraspinous fossa.

Reflect trapezius and deltoid to see it.

Powerful Lateral Rotator

ROTATOR CUFF MUSCLE.

Inserts into greater tubercle of humerus.

Infraspinatus.
-forms part of rotator cuff too!
-occupies infraspinous fossa (below spine of scapula) this is also partly covered by deltoid and trapezius, so these two need to be reflected to see infraspinatus.
-it is a powerful lateral rotator of humerus.
-to test it, flex elbow with arm adducted and rotate the arm laterally against resistance. the muscle can be palpated inferior to the scapular spine.
-originates form the infraspinous fossa. inserts into greater tubercle of huemrus (just posterior to supraspinous insertion).
-also intervated by suprascapular nerve
-rotates arm laterally and helps to stabilize humerus in the glenoid cavity.

Teres Minor

Thin band often not distinct from the lower edge of the Infraspinatus.

Works with infraspinatus to laterally rotate the arm.

Rotator cuff muscle too!

inserts into ______ of _____

Teres Minor

Thin band often not distinct from the lower edge of the Infraspinatus.

Works with infraspinatus to laterally rotate the arm.

Rotator cuff muscle too!

inserts into greater tubercle of humerus.

Teres minor.
-Also contributes to the group of muscles known as the Rotator Cuff muscles.
-narrow muscle that is not distinct from intraspinatous. lies along inferior border of infraspinatous and having the same action as that muscle.
-inserts on greater tubercle of humerus inferior to the insertion of the infraspinatous.
-so, that means 3 of rotator cuff muscles sit on greater tubercle ( Supraspinatous, infraspinatous and teres minor) .
-Origin of teres minor is on lateral border of dorsal surface of scapula (posterior surface).
-it inserts onto greater tubercle of humerus just inferior to the infraspinatious. -intervated by axilary nerve (branch of brachioplexis).
-Action is the same as infraspinatous (rotates the arm laterally and helps to stabalize the humerus in glenoid cavity)

Rotator Cuff Muscles

There are 4.

All are rotaters of humerus except one.

-Rotator cuff muscles can also be called the "Scapulo humeral muscles". this is because they extend from scapula to humerus.
- They are: supraspinatious, infraspinatous, teres minor, and subscapularis (aka ____ muscle)
- THey form a musculotendonous rotator cuff around glenohumeral joint (or the shoulder joint) . together they have an essential steadying affect on the head of the humerus.
-All except supraspinatous are rotators of humerus .
-the supraspinatous initiates abduction of humerus for the first 15 degrees. and then afterwards, deltoid does the rest.
-The tendons of 4 rotator cuffs blend with articular capsule of the shoulder to reinforce it and protect the joint as well as give it stability.

3 muscles of the rotator cuff insert on the greater tubercle of the humerus.

Where do these 3 sit?
where does the 4 th muscle insert?

3 in the greater tubercle of humerus are
-Supraspinatus
-Infraspinatus
-Teres Minor

Odd ball = SUBSCAPULARIS. inserts onto lesser tubercle.

Rotator cuff Muscles - ACTIONS

Supraspinatus:
Infraspinatus:
Teres Minor
Subscapularis:

All --> Tonic contraction to hold humeral head.

Most commonly injured? Supraspinatus.

Rotator cuff Muscles - ACTIONS

Supraspinatus: initiates abduction
Infraspinatus: lateral rotator
Teres Minor: lateral rotator
Subscapularis: medial rotator

All --> Tonic contraction to hold humeral head.

Most commonly injured? Supraspinatus.

Review on rotator cuff muscles actions.
Supraspinatus: not really a rotator.
Infraspinatus: aided by TM.
Subscapularis: primary medial rotator of humerus.
Together: they are all in tonic contraction (slightly contracted) to help hold and stablize humeral head.

Rotator cuff injuries.
-causes instabilities of shoulder joint (glenohumeral joint).
-acute tears occurs when an arm is violently pushed into abduction (hockey player being checked into boards..arm as a cushion)
-common in swimmers, pitchers, 3rd basemen who throw ball hard.
-injuries to rotator cuffs may follow dislocation of humerus.
-degenerative tendentious is common in older people. test for this by asking to lower abducted arm from a 90 degree angle. if there is disease/injury, the limb will suddenly drop to the side uncontrollably if rotator cuff is torn.
-supraspinatus is most commonly injured.

Teres Major

Helps form Posterir Axillary fold.

Works with _______________

Holds _______________ in place against pull of ____________.

Teres Major

Helps form Posterir Axillary fold.

Works with Latissimus Dorsi

Holds head of humerus in place against pull of Deltoid.

-teres major is thick and rounded. it means cylindrical in shape. it forms a rounded area on the inferior lateral third of the scapula when arm is abducted against resistance.
-teres major adducts and medially rotates arm. stabilizer of humeral head. holds it in place against pull of deltoid.
-origin is off the posterior surface of scapula along the inferior angle.
-it inserts into the intertuburclar sulcus of the humerus.
-it's tendon often fuses with the latisimus dorsi.
-it is intervated by the subscauplar nerve.
-it adducts extends and medially rotates the arm (similar to the latisimus dorsi..hence the Teres major is refered to as the latisimus dorsi's little helper since it does the same thiing)
-it's important to know that the teres major and teres minor have DIFFERENT NERVE SUPPLIES AND DIFFERENT ACTIONS.

3 muscles insert into intertubercular groove of humerus

Pectoralis Major
Latisimus Dorsi
Teres Major


All inserts into intertububercular groove of humerus.

anterior view of humerus. 3 muscles insert very close. green arrow is toward body (adduction). this shows where the 3 go.
-how to remember this? there is a major on either side of latissimus dorsi. two majors walking a lady.

Coracobrachialis

It is the Superior and Medial part of arm.

Often fuses superiorly witth _____

Coracobrachialis

It is the Superior and Medial part of arm.

Often fuses superiorly with short head of biceps brachii.

Located in the superior and medial part of the arm.
-extends from coracoprocess to the arm (aka brachium).
-name is from it's attachment sites.
-important landmark for brachioplexis..since one of the nerves of the brachioplexis (musculotitaneous nerve) pierces it aka runs right through it.
-the coracobrachialis helps to flex and adduct the arm.
-originates from the coracoid process of scapula and inserts on the medial surface of humerus just opposite the deltoid tuberosity.
-intervated by the musculotutaneous nerve (branch of the brachioplexis).
-it flexes and adducts the arm.
-the bicep brachii's short head is often fused with the coracobrachialis. you can differentiate by following them distally and seeing where they separate.

which muscles do what?
-for shoulder joints, think of which do flexion, which do extension, abduction, adduction,

think of rotation.
-which are lateral rotation of humerus and which are medial roation..?

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